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The goal of our research is to calculate runoff of global fallout cesium-137 from the Ob’ estuary macroarena. It includes the Ob’ river basin (83% of macroarena total area) and smaller river basins. Total storage of global fallout cesium-137 is 360 kCi in the Ob’ estuary macroarena according to our calculation based on GIS-research and latitudinal distribution of radionuclides from atmospheric nuclear tests. The tenth-order river basins (n=154, Horton coding system) shape 20 groups due to transfer and accumulate properties of topsoil as applied to cesium-137 global fallout. Six 1st order tributary river basins, characterized five groups of tenth order tributary river basins, were studied and 600 bulk core soil samples were collected in 2011 and 2012. The data obtained show that global fallout 137Cs runoff from undisturbing humid first order tributary river basin is less than 0,02 TBq/sq.km. Runoff from arable semi-humid first order tributary river basin varies from 0,1 to 1,3 TBq/sq.km. Internal flow areas occur 23% of the macroarena total area and accumulate whole cesium-137. Humid and semi-humid river basins cover 40% and 8% of study area respectively. We assume these basins yield the main contribution in cesium-137 runoff from the macroarena. Global fallout cesium-137 runoff summarized is 13-310 TBq (0,4-8,4 кCi) from humid and semi-humid river basins. There is 0,1-2,2 % of global fallout 137Cs total storage in the Ob’ estuary macroarena.